Change IsMethodTracingActive to GetMethodTracingMode.

This allows traceview to tell whether tracing is active, and whether
it is sampling or method tracing.

(cherry picked from commit 9d3a0a2e253aecd07c4a053c19cf9b0ccaa2db49)

Change-Id: I7e00f90f80de248f07dfa94d7d0f028931e1a716
4 files changed